1. Field of the Invention
The present invention relates to a printer such as an electronic typewriter, and more particularly to servo control of the velocity of a motor which selects a type of a type head (type wheel) or moves a carrier carrying the type head.
2. Description of the Prior Art
A D.C. motor is usually used as a carrier motor (or a type selection motor in a daisy wheel type head) of a printer such as an electronic typewriter. A target velocity of the carrier (type wheel selection motor) is set to follow a root curve, that is, it is proportional to the square root of a distance (rotation angle) from a current position to a target print position of the carrier (motor), and the velocity of the carrier (motor) is controlled in accordance with that curve. However, means for moving the carrier (motor) to follow the target movement (rotation) velocity cannot fully compensate for a change of friction of a load (friction of the motor and moment of inertia of the type head). As a result, the time required to move (rotate) the carrier (motor) by a given distance (angle) is not uniform, and if deceleration is not sufficient, overshooting occurs for the target print position and the print quality is degraded.